I was told that my S&W M&P Sport was an H-BAR, but it was sold to me as regulated. I see nothing on the rifle itself that states "H-BAR". I'm not sure if it is or not.
MH
If it has a stepped or contoured barrel, e.g. gets thinner in sections, as opposed to a solid single diameter heavy barrel, it is regulated.
This does not necessarily mean a huge varmint or bull type barrel.
Check out the Colt 6721, which though an LE gun can be sold unregulated,
(for now...)
http://www.colt.com/ColtLawEnforcement/Products/ColtTacticalCarbine.aspx
AS opposed to the model 6920, regulated.
http://www.colt.com/ColtLawEnforcement/Products/ColtLawEnforcementCarbine.aspx